Lens and lens mount



May 5, 1941, F. A. BANGERT ET AL 2,240,827

LENS AND LENS MOUNT Filed Sept. 9, 1958 2 Sheets-Sheet 1 I ATTORNEY May 6, 1941. A BANGERT ETAL 2,240,827

LENS AND LENS MOUNT Filed sept. 9. 193e l2 sheets-sheet 2 5f A @5mi W3 yf @2, *y2

\ INVENTCIRS Patented May 6, 1941 i LENSVAND LENS MOUNT Frank A. Bangert, Buffalo, Ralph K. Day, Snyder,

and Thomas G. Aitcheson, Kemnore, N. Y., and

.Lawrence J. Davenport, Long Beach, Calif., as- I signors to Spencer Lens Company, Buffalo, N. Y., a, corporation of New York Application september 9, 193s, serial No. 229,158

' (C1. ss-s'z) 8 Claims.

This invention relates to a lens and lens mount and more particularly to a plurality oflenses mounted in a single lens mount and adapted to be used in photographic work.

The prin-cipal objects of the invention are: A, to providea lens or lens mount in which each lens is automatically aligned axially during the assembly operation without requiring that its periphery be formed concentric with the optical axis yof the lens; B, to effect this .automatic centerngfwithout requiring that the mechanical parts involved be machined to close tolerances; C, to trap `all light rays which travel longitudinally outside of the optic-al apertures'of the lens and lens mount; D, to absorb such grazing and reflected rays .as would otherwise be deflected into the main stream of light rays and .thereby impair "the clearrless of the 'final image form; E, to provide an improved process of making the lens whereby the peripheral edge -of the lens is so re-enforced that chipping of its .edges during the grinding operation is prevented; F, to provide 20. The reason Why theldiameter of .this lens is sm-aller than the bore of the casing is because in the present invention the periphery of the lens is not ground and is not relied upon to axially align the lens, this alignment being effected by mechanically shifting the 1ens`laterally until it is in axial alignment. Hence, it is necessary to provide a sufficient clearance between the lens and the casing to permit of such a lateral movement.

ADisposed against the rear face of aforesaid double convex lens 22 is a centering ring 23, the periphery of which is a hard push fit in the bore of the casing 20. When this centering ring 23 isv pushed forcibly forward (to the left) the doulble convex lens 22 is caught between the front,

' mencement `of this movement of the centering inner edge of said ring and rear inner edge of the flange 2| f the casing 20. If at the comring 23 it -so happens (as it` usually does in actual practice) that the lensl 22 is axially out of such an optical arrangement as will -permit a" pair of lenses to b'e placed in .firm contact with each other and still be free to move laterally. relatively to each other; G, to provide a mechanical means Aof centering a lens with reference to one mechanicalsurface only; and H, to Iprovide a means for mechanically centering a. lens without subjecting said lens to any unsymmetrical internal strains. l

Other collateral objects of the invention and practical solutions thereof are disclosed in'the accompanying specification and illustrated in the f drawings wherein: t

Fig. 6 is a vertical, transverse section of the form of lens and lens mount shown in Fig. 5, taken on line 6 6 of Fig. 5.

Figs. 712`fare Vertical longitudinal sections through additional various forms of our improved lens and lens mount. l

Similar letters of reference indicate like parts l rthroughout theseveral figures of the drawings.

'Referring to Fig. `1 the numeral 28 represents left end thereof.` Adapted to be positionedV against the rear edge of -said v'lange 2| is a double convex lens 22, the outer diameter of which is somewhat smaller'than the bore of said .casing line, .the continued forward movement of said centering ring 23 will wedge over said lens in the one or other direction until all of the radially wedging forces imposed upon it are balanced. When this occurs the lens 22 is optically in line with the axis of the casing 20, inasmuch as its optical axis is necessarily coincident with those two radii of the .two faces which lie in one common straight line. Hence, said lens 22 is optically aligned with the casing 20 entirely irrespective of the form or shape of its periphery, providing, of course, that the lens is not so eccentric as to permit its periphery to come into actual contact with the bore of the casing 20 or to permit the inner corners of the flange 2| or centering ring 23 to slide inside the periphery of the lens.

The outer rear edge of the centering ring 23 is annularly rabbeted to form a narrowannular centering ring 24. The latter fbears against the front concave ia'ce of theconcavoconvex lens 25. Disposed rearwardly ofthe latteriis a -plano convex lens 26 and between the latter and the aforesaid concavo convex lens is arranged a centering ring 21. This latter ring is split diagonally at 28, the purpose of this split being to `pervmit, the ring to be made slightly over-size so as to have its periphery snugly in contact .with the bore of the casing 20 and thereby be positioned accurately concentric with the axis of said cas.- ing 20, even though the manufacturing tolerances of both the ring and the casing are'very large. I t will be noted that when the concavo convex lens 2 5 and the plano convex lens 26 are front centering ring 23.

pressed toward each other, the convex surface of the former imposes an outward thrust on the centering ring 21 and thereby presses the former in contact with the bore of the casing 2|).-k This insures that the centering ring 21 will remain circular even though it is the natural .tendency when distorted to assume a shape which is not circular butis moreor less egg-shaped.

The reason why the other centering ring 23 is not split is because if it were split the concave surface of the concavo convex lens 25 would tend to push the centering ring 23 inwardly away from the bore of the casing 20 and thereby tend to render said centering ring unsymmetrical with respect to the axis of the casing 20.

It will be noted that the split 28 of the centering ring 21 is arranged obliquely with reference to the axis of said ring. The purpose of this oblique split is to prevent rays of light from passing longitudinally through the ring exteriorly of its bore; i n

Disposed against the rear convex face of the l plano convex lens 26 is a clamping ring 30 whose periphery is threaded to engage with a suitable female thread 3l formed in the bore of the casing. When this clamping ring is tightened up, as for instance by engaging its slots 32 with a suitable spanner wrench, all three lenses, 22, 25

and 26 and both of the centering rings 23 and 21 are clamped between the ange 2| of the casing and aforesaid clamping ring 38. The double convex lens 22 is caused to automatically center itself by reason of its being clamped between the casing flange 2|- and the front inner edge of the The concavo convex lens 25.is similarly centered between the rear inner edge of the front centering ring 23 and the front inner edge of the rear centering ring 21. With reference to the plano convex lens 26, the rear centering ring 21 acts only as a spacing lring, all automatic centering being derived from the front inner edgeof the threaded clamping ring 3U.

Particularly when grinding the concave faces of'lenses such as the concave face of the concavo convex lens 25, there is a very marked tendency to chip the peripheral edges of the lens unless the grinding pressure is very low and the abrasive very soft and fine. This causes an` undue slowing down of the speed of the grinding operation. The present invention eliminates this difficulty by supplying the periphery of each of the lenses with a reinforcement 29 which is preferably sufficiently black and dull in color to absorb such grazing and outwardly directed rear face of this lens 35 is a spacing sleeve 36 whose rear face in turn bears against the front i face of the plano convex lens 31. The rear face of the latter bears against and is centered by ing ring 39. It will be noted that the spacing sleeve 36'is out of contact with the bore of the casing 33 and that, therefore, it is centered by the rear face of the double concave lens 35 and ac ts only as a spacing member, the position of sald front lens 35 being solely a function of the position of the casing flange 34, and the position of the rear lens 31 being'solely a function of thecentering ring 38.

In Fig. 3 is shown a construction suitable for optical systems in which the lenses are too close together to permit of a spacing ring. In this case the rear face of the front concavo convex lens 40 is in direct contact with the front face of the rear concavo convex lens 4|. In this ca se the two lenses are caused to be axially allgned relative to each other by direct contact with each other and at the same time each lens 1s independently axially aligned by the flange 42- and -the clamping ring 43 respectively.

In Fig. 4 is shown a construction in which the front lens 44 isaxially aligned by solely one reference point; namely, the casing -lange 45, whlle the rear lens 46 is located by the centering rlng 41 and the clamping ring 48. This figure also illustrates how a number of lenses may be combined with a :flat member such as the heat absorbing glass disc 49 which is not centered at all but does act as-a spacing member in combmation with the spacing sleeve 50 l friction between any two certainlenses is so great that they cannot be accurately centeredl when the construction of Fig. 3 is employed. In

f such an event a construction such as that shown 1 in Figs. 5 and 6 may be adopted. In this case the front concavo convex lens 5| is not in direct contact with the rear concavo' convex lens 52. Instead, the latter is enameled on its front face at 53 prior to the grinding of the lens and then,

` after the two faces of said lens have been'ground,

forcement 29 is, of course, applied to the periphery of the lenses prior to the grinding operation, and it may be applied in the form of black enamel in powder form, and the lenses then heated to melt the enamel, or it may be applied in molten form, 'preferably while the lenses are still hot. In the latter case, if these hot lenses are sent to the annealing lehr, the enamel will be baked simultaneously with the annealing of the lenses with no additional heat required for the enamel Aits front end which engages the f ront face of a double concave lens 35. Bearing'against the the lens is chucked up coaxially with the common optical axis of its two faces and the fiat,

enameled face 53 then trued up. Thereafter when the two lenses 5| and s2 areassemmed in their casing 54, the front lens 5I makes contact with the enameled face 53 of the rear lens 52 and does not make contact with the lens v52 itself. It is to be understood, of course, that such an enamel should be chosen for the face 53 of lens 52 as-Will have a smaller coeicient of friction with the glass of the front lens 5I than the glass of the rear lens 52 would have with the glass of said front lens.

In the manner' in which lenses arev ordinarily mounted, the lenses are subjected to bending strains (in addition to their normal compression strains) unless the metal parts are machined :within extremely fine limits. Figs. 5 .and 6il vnularly against the front lens 5I but instead it' is provided with an annular row of three equallyv spaced legs 51 whoserear ends bear against the front face of the-front lens at three points and subjects said lens to substantially compression loads only.

Fig. 'l illustrates a pair of lenses 58 and 59 mounted in .a casing 60. The front lens 58 is automatically centered between an integral flange 6I of the casing 60 and the front inner edge lof a spacing ring 62. The rear lens 59 is automatically centered between the rearv edge of the aforesaid spacing ring 62 and the front inner edge of a clamping ring 63. The latter is threaded at its rear end into. the casing 60, but its front endA atv 6l`is turned down somewhat and engages 'the smooth inner bore ofthe casing 68 and thereby acts as a pilotfor centering clamping' ring 63. This permits the screw threads' of said clamping ring 63 and the threads of the cassecting points of contact between its pilot portion 80 'or 8| and the aligning bore 86 or 61 of the casing 88.'

i clamping sleeve 92 is unprovided with a pilot but instead is ,caused to'be coaxial with the bore of the.casing 93 by reason of the relatively long ing '60 -to be machined in a relatively coarse.

fashion and still causing the .clamping ring 63 to be very accurately aligned withrespect to the casing 68. This form of "clamping ring has been found in actual practice to very accurately align any glass lens which has a Vreasonably small radius of curvature upon its one or other-face.

Fig. 8' issimilar to Fig. '7, except that the rear lens 65 is a double concave lens instead of a double convex lens asin Fig. 7. It has been found in actual -practice of utmost importance that the lenses being automatically centered be clamped at points equi-distant from their optical axes.. In this Fig. -7 is shown how each lens 66 and 65 isindividually gripped by means which are equi-.distantfromv its optical axis and that in addition to this both lenses' are gripped by means which areequi-distant from their optical axes. Why this factor `should be so important is not at present clearly understood, `out .that it'is lof great importance has been very deiinitely' ascertained.

and very. accurately machined threads 94. This construction also shows 'how two lenses, such as the lenses 95 and 96, may be pressed substantially in face to face contact and yet be free to move laterally with respect to each. other without un.

due friction. 'This is effected by placing a metal ring 91 on the frontperipheral edge of the rear lens 96, the inner portion of said metal ring 91 being flared inwardly and rearwardly so that when the 'two lenses 95 and 96 are placed together with this ring 91 between them, said lring is prevented from being laterally displaced by reason of its ared'shape.

It is to be understood that this invention is not to be confined to the particular forms herein illustrated and: described, but. is to include all Fig. 9 shows a construction which is somewhat similar to that of. Fig. 7 except that each lens 61 and 68' is individually gripped by the clamping rings 69 and 10 respectively. It will be noted that the notches 1I -of clamping ring 18 (which are used l,for tightening said clamping ring) are omitted. from the clamping ring 69 and replaced by. a pair of longitudinally formed holes 12 for the reception of 'a suitable Spanner Wrench.- This use of the holes 121for tightening the front clamping ring 69 provides a smooth continuous edge of contact between. said front clamping ring 69 and the rear lens 68. This contwo lenses 61 and 68. in the casing 13 much' more struction shown in Fig. 7.

Fig. 10 shows a construction which is somewhat similar to that -of Fig. 7 but shows how thel casing 14 may be somewhat reduced inlength,

by having the clamping ring 15 extending r-forwardly beyond therear face of the rear lens 16. In this case the clamping ring 15 vhas its threads 11 formed at its front end and its pilot portion 18 formed at its rear end.

Fig. 11 illustrates a construction in which the" "65' cylindrical pilot portions 80 and`8| of the clamping rings 82 and 83 are disposed at the front end of said clamping rings and exteriorly thereof. Thisv is eifected by .arranging th'e lenses 84 and 85 within the front ends of said clamping rings. This permits of-having relatively llong pilots so that the clamping ringsare not only aligne'd laterally but are also prevented Irom cocking. `With thisv arrangement all points'of contact between each lens` and its companion clamping ring lies in a transverse plane interthe bearing edge of' said ring, whereby said' lens struction of Fig. 9 has beenfound to alignthe 'l accurately than with the less expensive con" lenses and/or lens mounts encompassed by the 'following claims.

. We claim:

1. A casing for a lensmount having a cylindrical bore; a centering means carried in said bore l and formed of a ring axially movable in said bore and having a lens-bearing, circular, contacting edge disposed perpendicularly of the axis of the casing and spaced from said casing; a lens in said casing; retainingmeans in said casing to hold said ring and lens in substantial contact around is optically'centered with its axis parallel 4to axis of the bore of saidcasing.

2. A casing for a lens mount having ya cylindrical bore; a centering means carried in said bore and formed of a ring axially movable in said the bore and having a'lens-bearing; circular, contacting edge disposed concentric to the axis of the casing; said ring having a cut back portion adjacent its lens contacting edge;'.a lens in -said casing; retaining means in said casing to hold said ring and lens in .substantial contact around l the bearing edge of 'said-ring whereby said lens is optically centered with its axis coincident with theaxis of the bore of said casing.

3. A casing for a lens mount having a cylindrical bore; a centering means carried in said `bore and formed of a ring axially movable in said bore and having a lens-bearing, circular,

4:contacting edge disposed perpendicularly of the axis'of the casing;.. saidring having a cut back portion adjacent its lens contacting edge; a lens having a concaveface arranged in said casing;

'y retaining means in said casing to hold said ring and lens in substantial contact around the bearing edge of said ring, whereby said lens is optically centered With its axis parallel to ythe axis of the bore of saidl casing.

4. A casing for a lens mount having a cylin'- dricalbore; a centering means carried in said bore and formed of a ring axially movable in said' bore and having a lens-bearing, circular, contacting edge disposed perpendicularly of the axis of the casing; said-,ring having a cut back portion surrounding its lens contacting edge; a double convex lens in said casing; retaining means in said casing to hold said ring and lens in substantial contact around the bearing edge of said ring, whereby said lens is optically centered With its axis parallel to the axis of the bore of said casing.

5. A lens and lens lmount comprising: a. tubula'r casing; a lens having a curvilinear face and having a diameter appreciably smaller than the bore of said casing; means connected with said casing and arranged to restrain longitudinal movement of said lens; a split centering ring arranged within the bore of said casing and vonly bearing against the curvilinear face of said lens inwardly of its peripheraledge; and means connected with said casing and arranged to press the centering ring toward the lens.

6. A lens and lens mount comprising: a. tubular casing; a lens having a curvilinear face and having a diameter appreciably smaller than the bore of said casing; means connected with said casing and arranged to restrain longitudinal movement of said lens relatively Ato said casing; an obliquely split centering ring arranged Within the bore of said casing and only bearing against the curvilinear face of said lens inwardly of its peripheral edge; and means connected with said casing and arranged to press the centering ring toward the lens.

. casing and only bearing against the curvilinear facevof said lens inwardly of its peripheral edge,

the expanded diameter of such centering ringbeing larger than the bore of said casing; .and means connected with said casing and arranged 'to press the centering ring toward the lens.

8. A lens and lens mount comprising: a tubular casing; a lens having a diameter appreciably smaller than the bore of said casing; means connected with said casing and arranged to restrain ylongitudinal movement of said lens relative thereto; a second lens having a curvilinear face an-d also having -a diameter appreciably smallerl than the bore of said casing; an anti-friction ring arranged between said lenses; and centering means connected with said casing and only bearing against the curvilinear face of the second named lens inwardly of its peripheral edge.

FRANK- A. BANGERT. RALPH K. DAY.

THOMAS AITCHESON. LAWRENCE J. DAVENPORT. 

